In laser processing procedures it is often desirable and even necessary to ascertain the temperatures within a predefined processing region during the processing operation in order, for example, to be able to make inferences regarding the particular quality to be adhered to during the processing operation and the adherence to specific processing regions, but also for the feedback control for the processing operation.
Since during the processing operation the temperatures at the different positions of a respective processing region vary locally and over time in dependence on a number of parameters such as, for example, the respective laser output power used in the processing operation, the deflection speed and/or direction of laser beams, and the respective workpiece to be processed, space-resolved determination of temperatures within a processing region is desirable.
Known systems measure and assess the welding process with individual photodiodes or CCD/CMOS cameras. In that method, infrared radiation is captured in the form of a simple radiation intensity measurement. In the case of those radiation measurements, inter alia absolute temperature, emission coefficient, illumination of the measurement field etc. are superposed. Furthermore, radiation intensity measurements are highly dependent on fouling of the optical systems, smoke and plasma in the observation beam path. Assessment of a process using intensity measurements is therefore inaccurate.
An arrangement for space-resolved temperature measurement is known from DE 10 2004 051 876 A1, wherein a predefinable processing region of a workpiece can be imaged onto an optical detector measuring in a space-resolved manner, and at least one optical filter that blocks the electromagnetic radiation of one or more laser processing beams is disposed in the beam path between the processing region and the optical detector.